Soil fungi could help us fight global warming

It is no longer enough to simply reduce the amount of CO2 we pump into the atmosphere: to cope with climate change, we need to reduce the amount that is already there. Although many strategies are needed to reduce greenhouse gas (GHG) emissions, soil carbon sequestration – an important part of the Australian Government’s plan for net-zero emissions by 2050 – can provide an important contribution.

The 2018 SCINEMA International Science Film Festival Winner of Best Documentary and Audience Award Based follows a journey to bring such a strategy to the world: using fungi to remove carbon dioxide from the air and store it in agricultural soil. Almost four years after the film’s debut, where does that strategy stand now?

What is soil carbon sequestration?

Soil carbon sequestration works by removing CO2 which is already present in our atmosphere, then converts it into a stable form of carbon which can then be stored in the ground for the long term. There are different approaches to achieve this, but the one described in Based explores the use of endophytic fungi to turn Australia’s vast farmlands into our greatest potential carbon sink.

“Soil is the largest terrestrial carbon sink on the planet, managed by the people who have the most to lose from climate change; farmers,” said agronomist Guy Webb, featured in Based, to the Australian Science Channel in 2019. “We hope our trials will show that it can be easy and economical for them to transfer carbon from the air and fix it in their soil.”

In the film, the strategy promised to be a fast-paced, globally scalable carbon removal solution that also delivered huge benefits to growers who implemented it. But how does it work?

How does carbon sequestration work with mushrooms?

The strategy is reminiscent of the already common agricultural practice of the inoculation of legume and legume crops with Rhizobia bacteria that fix atmospheric nitrogen in the soil.

Instead, a farmer coats his seeds with a microbial inoculum before sowing. This coating contains melanized endophytic fungusa type of symbiotic fungus that then grows in the roots of plants after they germinate.

Credit: Andreas Reh/Getty Images

As the plant absorbs CO2 from the atmosphere and produce simple sugars in the soil (in a process called photosynthesis), fungi work to convert them into melanin – a complex and more durable carbon compound. It is safely deposited in tiny, compressed soil particles called microaggregates where, once trapped inside, the carbon is stable in the soil and can be stored long term.

“Endophytic fungi potentially have a role to play, particularly in converting carbon to more stable melanized forms of carbon that will resist decomposition and stay in the soil longer, thereby enhancing sequestration,” says Dr Michael Crawford , Managing Director of Ground CRCwho has more than 25 years of experience in research and scientific management in fields related to soil science.

However, not only do you get the benefits of climate change mitigation by removing excess CO2 of our atmosphere, but soil conditions are also improving when enriched with carbon, resulting in increased water retention, nutrient availability and improved soil structure for root growth.

This is particularly important for growers in Australia, as farming takes place on land that has problems with soil quality and water shortage. But where has this technology been in the past four years? And is it close to being widely available?

What has happened since Based?

There have been some exciting developments in the four years since Based has been freed. Progressing by leaps and bounds, the startup Organic lemon (previously Soil carbon Co) raised $50 million from investors since it was formed.

Co-founded by Guy Hudson, Tegan Nock, Frank Oly, Mick Wettenhall and Guy Webb – names you might recognize Based – the start-up is based in Orange in the Central Tablelands of New South Whales. They now employ over 35 people in four different laboratories and 25 field sites in Australia and the United States.

Loam Bio has been busy researching which inoculum is best at sequestering carbon, taking thousands of fungal samples from across Australia and sifting through a library of more than 1,500 microbes to put them to the test.

Using bioinformatics analysis to study microbial genomes, along with extensive field testing, they also determined which combinations of fungi and bacteria are most optimal to market, so that the product that hits the shelves can be accessible to all. Farmers.

However, according to Crawford, many challenges need to be addressed for endophytic fungi to be effective in practical agriculture.

“The comparison with inoculation with Rhizobium bacteria is relevant to some extent, but fungi have many critical differences from bacteria – size, morphology, life cycle, etc.,” he says. “Success depends on the ability to introduce live microorganisms into a soil environment that experiences extreme conditions (wet/dry, hot/cold, acidic, sodic, etc.), and for the fungi to successfully compete for resources against microorganisms that are endemic (and adapted to) that environment.

“Obviously, the conditions must be optimal for endophytic fungi to be successfully introduced in order for them to survive and thrive. This will not always be the case.

“More field trial results are needed to determine the consistency of benefits, across a range of soil types, climates, farming systems, etc. to better understand the feasibility of implementation. It’s starting to happen.

So, it looks like for now we’ll have to wait and see if the technology can overcome these hurdles. Luckily, we may not be waiting long; In 2021, Tegan Nock, product manager at Loam Bio, told ABC News that the company aimed to have a product widely available on shelves by 2023.

How does the use of mushrooms compare to other carbon sequestration practices in Australia?

Credit yuelan getty images 850
Credit: yuelan/Getty Images

According to Crawford, to say that endophytic fungi alone could stave off global warming is hyperbole — there’s simply no silver bullet to climate change. Instead, it is important that we build a broader repertoire of practices, of which soil carbon sequestration with endophytic fungi may be just one of many strategies.

“It’s critical that research into technologies like this continue, especially given the focus on a technology-driven response to climate change,” says Crawford. “In reality, it is likely that practices such as melanized endophytic fungi will contribute to soil carbon sequestration, as well as practices such as zero tillage, stubble retentionsummer crop, double crop, perennial pastures, intercroppingremoval of soil constraints etc, but this will not be the only solution.

“Regardless of the benefits of climate change, any practice that leads to higher levels of organic matter in the soil will also lead to increased water infiltration and retention, improved soil structure, improved biological activity and nutrient availability over the longer term, and will be good for soil health and agricultural productivity more generally.

“Which is very good.”

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Teresa H. Sadler